CN101642858A - Nuclear shell structure Pb-free solder ball for electronic packaging and preparation method thereof - Google Patents
Nuclear shell structure Pb-free solder ball for electronic packaging and preparation method thereof Download PDFInfo
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- CN101642858A CN101642858A CN200910091758A CN200910091758A CN101642858A CN 101642858 A CN101642858 A CN 101642858A CN 200910091758 A CN200910091758 A CN 200910091758A CN 200910091758 A CN200910091758 A CN 200910091758A CN 101642858 A CN101642858 A CN 101642858A
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Abstract
The invention relates to a nuclear shell structure Pb-free solder ball for electronic packaging and a preparation method thereof, belonging to the technical field of Sn-based Pb-free brazing alloy. The solder ball contains the following chemical components by mass percent: 47-68% of Bi, 19-32% of Cu, 13-21% of Sn and 0.01-1% of rare earth metal. The diameter of the solder ball is 0.10-0.76mm. Thesolder ball has a nuclear shell structure, the nuclear core is a Cu-rich phase, and a layer of Sn-Bi-rich alloy is evenly coated on the shell. The Pb-free solder ball of the nuclear shell structure can be applied to BGA packaging. Peripheral low-melting point SnBi alloy mainly plays a role of connecting components in jointing, while internal high-conductivity Cu-based alloy plays a role of circuitconnection, which can meet the demands of high connection strength, high conductivity and high heat conductivity of electronic packaging.
Description
Technical field
The invention belongs to the tin base leadless soldering-flux technical field, particularly a kind of nuclear shell structure Pb-free solder ball for electronic packaging and preparation method thereof.
Background technology
At present, BGA Package (BGA encapsulation) becomes the main flow of Electronic Packaging technology just gradually, thereby this technology is exactly to adopt solder ball to replace pin in the IC component packaging structure to satisfy the Electronic Packaging mode of electrical equipment interconnection and mechanically interconnected requirement, and one of its core technology is exactly the preparation of high-quality solder ball.Solder ball in the market mostly is the Sn-Pb alloy, because lead and compound thereof belong to extremely toxic substance, human health and environment is had very big harm.At present all or made laws and forbidden that production and selling has kupper solder in countries in the world, thus the research of having quickened lead-free solder to seek a kind of suitable Sn-Pb scolder substitute, solder ball faces unleaded pressing for too.
The microstructure of existing Pb-free solder ball is homogeneous diametrically.Along with material science day by day to the trend development of multifunction, compoundization, the Pb-free solder ball with nucleocapsid structure comes out and is subjected to extensively attracting attention [I.Ohnuma, et al., Science, 297-9 (2002) 990 for C.P.Wang, X.J.Liu].The solder ball microstructure as shown in Figure 1, core is rich Cu phase, shell evenly wraps up the rich Sn-Bi alloy of one deck.This alloying pellet has very big application prospect in the Electronic Packaging field, the low melting point Sn alloy of periphery mainly works to connect components and parts during welding, inner high conductivity Cu base alloy is then born the function that circuit connects, and can satisfy the requirement of the high bonding strength of following Electronic Packaging, high conductivity and high heat conductance.The formation of nucleocapsid structure is because the Cu-Sn-Bi alloy is the ternary monotectic alloy, when solidifying in the miscible district of difficulty liquid phase separation takes place, minority phase (rich Cu phase) drop with matrix liquid phase (rich Sn-Bi mutually) thus interfacial tension exist gradient to produce the Marangoni convection current, minority phase drop forms nucleocapsid structure to central motion.
But the nucleocapsid structure solder ball diameter of present report is all less than 0.1mm, and the diameter that solder ball is used in the BGA encapsulation can't use between 0.10-0.76mm.If increase the solder ball diameter, can cause cooling velocity to descend, nucleocapsid structure lacks, and the interference of gravity increase, influences the parameters such as sphericity of solder ball.Therefore, be necessary very much to improve prior art, develop and satisfy the large scale nuclear shell structure Pb-free solder ball that current BGA encapsulation requires.
Summary of the invention
Order of the present invention is to provide a kind of nuclear shell structure Pb-free solder ball for electronic packaging and preparation method thereof, overcomes that the solder ball diameter is all little, cooling velocity descends deficiencies such as nucleocapsid structure disappearance.
Composition, the structure of Pb-free solder ball of the present invention are as follows:
(1) the solder ball chemical composition is 47～68%Bi, 19～32%Cu, 13～21%Sn; Add 0.01～1% rare earth element (mass percent), be rear-earth-doped ternary monotectic alloy.
(2) the solder ball diameter is at 0.10～0.76mm.Have nucleocapsid structure, core is rich Cu phase, and shell evenly wraps up the rich Sn-Bi alloy of one deck.
Theoretical foundation of the present invention is:
Calculate and experimental verification by theory, choose suitable rare earth element and content thereof, add in the Cu-Sn-Bi alloy, can increase liquid rich Cu phase and rich Bi interfacial tension gradient mutually, quicken the Marangoni convection current of rich Cu phase drop, impel that (0.10～0.76mm) solder ball also can form complete nucleocapsid structure in inside under lower cooling velocity, thereby realizes its application at the BGA packaging industrial than major diameter.
Theoretical calculating comprises with PHASE DIAGRAM CALCULATION method (CALPHAD) calculating Cu-Sn-Bi ternary phase diagrams (as shown in Figure 2), select suitable alloying component and content of rare earth according to the difficult miscible district in the phasor, also comprise with the Kaptay model and calculate interfacial tension, determine suitable rare earth element and content.
Experimental result shows, adds the rare earth of mass ratio 0.01～1%, can significantly promote the formation of nucleocapsid structure.Diameter is that the BGA solder ball of 0.10～0.76mm all can form complete nucleocapsid structure, even diameter also can form tangible nucleocapsid structure up to the alloying pellet of 5mm.As shown in Figure 3.
Solder ball of the present invention is prepared according to the following steps:
(1) alloy melting
In order to reduce the volatilization of Bi, adopt the two-step method molten alloy.The first step is weighed metal Cu and Sn in selected ratio, in the induction melting furnace of packing into, feed argon gas, is warming up to 1100 ℃ metal molten is cooled off then, repeats 2～4 times to mixing; In second step, metal Bi with rare earth is weighed in proportion and the melting once more together of the Cu-Sn alloy block of fritting, temperature is 800～1000 ℃.
Selected ratio is: the solder ball chemical composition is 47～68%Bi, 19～32%Cu, 13～21%Sn; Add 0.01～1% rare earth metal (mass percent).
(2) gas atomization
Melting uniform alloy melt flows out continuously equably; be atomized into the drop of disperse during by nozzle by high pressure argon gas or nitrogen fragmentation; drop is free-falling in atomization tank; under surface tension effects, be shrunk to complete sphere; cooling continuously naturally in protective atmosphere when falling; by the nucleocapsid structure of difficulty inner formation rule of miscible when district, finally be frozen into the solder ball of surface-brightening, diameter is between 0.10～0.76mm.Atomization pressure is 0.2～1.0MPa.
(3) collect, clean, dry,
Pb-free solder ball after the moulding washes with clear water, cleans 2～3 times with the ultrasonic cleaning machine again, and each 5～20 minutes, ultrasonic cleaning agent can be with pure water or acetone.Be 100～150 ℃ in temperature then, vacuum is to dry 10-60 minute under 1～8KPa condition.
(4) sieve, select and pack
Select the metal ball body of diameter between 0.10～0.76mm by screening machine or manual mesh screen, choose spherical complete, the flawless solder ball of surface-brightening, pack at 1～8KPa vacuum condition lower seal then.
The invention has the advantages that, prepare a kind of large-sized nuclear shell structure Pb-free solder ball, can be widely used in the BGA encapsulation.The low melting point SnBi alloy of periphery mainly works to connect components and parts during welding, and inner high conductivity Cu base alloy is then born the function that circuit connects, and can satisfy the requirement of the high bonding strength of Electronic Packaging, high conductivity and high heat conductance.
Description of drawings
Fig. 1 is the microphoto of the nucleocapsid structure Cu-Sn-Bi solder ball of bibliographical information, and diameter is no more than 0.1mm.Photo is from [I.Ohnuma, et al., Science, 297-9 (2002) 990 for C.P.Wang, X.J.Liu].
The Cu-Sn-Bi ternary alloy phase diagram of Fig. 2 for obtaining by the PHASE DIAGRAM CALCULATION method.
Fig. 3 is for adding the microphoto of the large scale nucleocapsid structure Cu-Sn-Bi alloying pellet that obtains behind the 0.05%Ce, and diameter is up to 5mm.
The specific embodiment
(1) alloy melting
Adopt the two-step method molten alloy.The first step was weighed metal Cu and Sn by weight 3: 2, in the induction melting furnace of packing into, feed argon gas, is warming up to 1100 ℃ alloy melting is cooled off then, repeated 3 times to mixing; Second step is in 1: 1.5 ratio weighing Bi piece of CuSn alloy.The rare earth metal that can effectively promote nucleocapsid structure to form comprises simple metal that following table is listed and composition thereof, and its addition is 0.05% (mass fraction), the melting once more together of the Cu-Sn alloy block of metal Bi, rare earth metal and fritting, and maximum temperature is 800 ℃.
(2) gas atomization
Melt uniform alloy melt and be atomized into drop, in atomization tank, cool off, solidify, form complete solder ball by the high pressure argon gas of 0.2MPa.
(3) collect, clean, dry,
Pb-free solder ball after the moulding washes with clear water, cleans twice with the ultrasonic cleaning machine again, and each 5 minutes is 110 ℃ in temperature then, and vacuum is to dry 20 minutes under the 2KPa condition
(4) sieve, select and pack
Manual mesh screen is selected the metal ball body of diameter between 0.10～0.76mm, chooses spherical complete, the flawless solder ball of surface-brightening, packs at 2KPa vacuum condition lower seal then.
Claims (4)
1, a kind of nuclear shell structure Pb-free solder ball for electronic packaging is characterized in that, the chemical composition of solder ball is: the solder ball chemical composition is 47～68%Bi, 19～32%Cu, 13～21%Sn; Add 0.01～1% rare earth metal, be mass percent;
The solder ball diameter is 0.10～0.76mm, has nucleocapsid structure, and core is rich Cu phase, and shell evenly wraps up the rich Sn-Bi alloy of one deck.
2, solder ball according to claim 1, it is characterized in that, described rare earth metal comprises: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y and composition thereof, the mass fraction hundred of interpolation is 0.01～1%.
3, the preparation method of the described nuclear shell structure Pb-free solder ball for electronic packaging of a kind of claim 1 is characterized in that, processing step is:
(1) alloy melting:
Adopt the two-step method molten alloy: the first step, metal Cu and Sn are weighed in selected ratio, in the induction melting furnace of packing into, feed argon gas, be warming up to 1100 ℃ metal molten is cooled off then, repeat 2～4 times to mixing; In second step, metal Bi with rare earth is weighed in proportion and the melting once more together of the Cu-Sn alloy block of fritting, temperature is 800～1000 ℃;
(2) gas atomization
Melting uniform alloy melt flows out continuously equably, be atomized into the drop of disperse during by nozzle by high pressure argon gas or nitrogen fragmentation, drop is free-falling in atomization tank, under surface tension effects, be shrunk to complete sphere, cooling continuously naturally in protective atmosphere when falling, by the nucleocapsid structure of difficulty inner formation rule of miscible when district, finally be frozen into the solder ball of surface-brightening, diameter is between 0.10～0.76mm; Atomization pressure is 0.2～1.0MPa;
(3) collection, cleaning, drying
Pb-free solder ball after the moulding washes with clear water, cleans 2～3 times with the ultrasonic cleaning machine again, and each 5～20 minutes, ultrasonic cleaning agent can be with pure water or acetone; Be 100～150 ℃ in temperature then, vacuum is to dry under 1～8KPa condition 10～60 minutes;
(4) sieve, select and pack
Select the metal ball body of diameter between 0.10～0.76mm by screening machine or manual mesh screen, choose spherical complete, the flawless solder ball of surface-brightening, pack at 1～8KPa vacuum condition lower seal then.
4, method according to claim 3 is characterized in that, described selected ratio is: the solder ball chemical composition is 47～68%Bi, 19～32%Cu, 13～21%Sn; Add 0.01～1% rare earth metal, be mass percent.
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Cited By (9)
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| CN102059471A (en) * | 2010-12-29 | 2011-05-18 | 厦门大学 | Soldering paste of Sn-Bi-Cu self-packed composite powder and preparation method thereof |
| CN102990243A (en) * | 2011-09-16 | 2013-03-27 | 赵明生 | Solder-alloy solder powder and manufacturing method and processing device for realizing same |
| CN103753049A (en) * | 2013-12-27 | 2014-04-30 | 哈尔滨工业大学深圳研究生院 | Cu@Sn core-shell-structured high-temperature solder and preparation method thereof |
| CN106544534A (en) * | 2017-01-13 | 2017-03-29 | 东北大学 | A kind of preparation method of the immiscible alloy with baseball composite construction granule |
| EP3225348A1 (en) * | 2015-07-08 | 2017-10-04 | Napra Co., Ltd. | Metal particles having intermetallic compound nano-composite structure crystal |
| CN107511603A (en) * | 2017-09-30 | 2017-12-26 | 北京康普锡威科技有限公司 | A kind of compound welding powder of core shell structure bimetallic and preparation method thereof |
| CN111112597A (en) * | 2020-01-16 | 2020-05-08 | 深圳第三代半导体研究院 | Ternary metal core-shell structure micro-nano particle and preparation method thereof |
| CN114654126A (en) * | 2022-04-29 | 2022-06-24 | 浙江亚通焊材有限公司 | Silver-coated copper soldering paste and preparation method thereof |
| CN115870667A (en) * | 2022-12-26 | 2023-03-31 | 中国科学院电工研究所 | Welding material for welding at temperature below 200 ℃ and high-temperature-resistant application, preparation method and joint preparation method |
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- 2009-08-27 CN CN200910091758XA patent/CN101642858B/en not_active Expired - Fee Related
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102059471A (en) * | 2010-12-29 | 2011-05-18 | 厦门大学 | Soldering paste of Sn-Bi-Cu self-packed composite powder and preparation method thereof |
| CN102059471B (en) * | 2010-12-29 | 2013-03-20 | 厦门大学 | Soldering paste of Sn-Bi-Cu self-packed composite powder and preparation method thereof |
| CN102990243A (en) * | 2011-09-16 | 2013-03-27 | 赵明生 | Solder-alloy solder powder and manufacturing method and processing device for realizing same |
| CN102990243B (en) * | 2011-09-16 | 2015-11-04 | 赵明生 | Manufacture method and the processing unit (plant) realizing the method for brazing filler metal alloy solder powder |
| CN103753049A (en) * | 2013-12-27 | 2014-04-30 | 哈尔滨工业大学深圳研究生院 | Cu@Sn core-shell-structured high-temperature solder and preparation method thereof |
| CN103753049B (en) * | 2013-12-27 | 2017-02-01 | 哈尔滨工业大学深圳研究生院 | Cu@Sn core-shell-structured high-temperature solder and preparation method thereof |
| CN107240440A (en) * | 2015-07-08 | 2017-10-10 | 纳普拉有限公司 | Metallic, paste, formed body and layered product |
| EP3225348A1 (en) * | 2015-07-08 | 2017-10-04 | Napra Co., Ltd. | Metal particles having intermetallic compound nano-composite structure crystal |
| US10016848B2 (en) | 2015-07-08 | 2018-07-10 | Napra Co., Ltd. | Metal particles having intermetallic compound nano-composite structure crystal |
| US10478924B2 (en) | 2015-07-08 | 2019-11-19 | Napra Co., Ltd. | Metal particle and electroconductive paste formed therefrom |
| CN107240440B (en) * | 2015-07-08 | 2019-12-10 | 纳普拉有限公司 | Metal particle, paste, molded body, and laminate |
| US10507551B2 (en) | 2015-07-08 | 2019-12-17 | Napra Co., Ltd. | Metal particle and articles formed therefrom |
| CN106544534A (en) * | 2017-01-13 | 2017-03-29 | 东北大学 | A kind of preparation method of the immiscible alloy with baseball composite construction granule |
| CN106544534B (en) * | 2017-01-13 | 2018-02-16 | 东北大学 | A kind of preparation method of the immiscible alloy with baseball composite construction particle |
| CN107511603A (en) * | 2017-09-30 | 2017-12-26 | 北京康普锡威科技有限公司 | A kind of compound welding powder of core shell structure bimetallic and preparation method thereof |
| CN111112597A (en) * | 2020-01-16 | 2020-05-08 | 深圳第三代半导体研究院 | Ternary metal core-shell structure micro-nano particle and preparation method thereof |
| CN114654126A (en) * | 2022-04-29 | 2022-06-24 | 浙江亚通焊材有限公司 | Silver-coated copper soldering paste and preparation method thereof |
| CN115870667A (en) * | 2022-12-26 | 2023-03-31 | 中国科学院电工研究所 | Welding material for welding at temperature below 200 ℃ and high-temperature-resistant application, preparation method and joint preparation method |
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| CN101642858B (en) | 2011-11-09 |
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